The first screening part was fine, and I got a take-home challenge. The timeframe was around 1 week without a strict deadline. After getting the assignment, they welcomed me to ask questions. The problem statement -- the definition of the input -- indeed needed some clarification. So I used the opportunity and sent a follow-up question. However, from that very moment the hiring manager disappeared. (Spoiler: she never appeared again). I made some assumptions and continued my work. A few words about the task. Without revealing the details (by ethical reasons), it was a difficult real-world problem. I approached it iteratively, providing a baseline and another a bit more complex and effective solution with code and documentation. Besides that, I provided my vision of possible approaches and an algorithm for the next iteration. It took significant amount of time, research, and effort. My research showed that, in general, the problem is not actually solved yet, there are only a few products addressing it, and all of them are experimental and commercial ones. A few weeks later, on linkedin, I found a research paper (not precisely on that topic, but close to it) proving that my suggested approach made a lot of sense. In the end, all my following e-mails were ignored, including the one with the delivery. --- The story got unexpected and hilarious continuation when another hiring manager contacted me via Linkedin and proposed to apply for exactly the same position. After my reaction, they apologized and explained the situation by some difficulties with a new HR software. Soon after, roughly within 30 minutes, I received a negative feedback on my assignment, stating that my solution was too simple. Despite they do provided some personalised feedback, which I appreciated, their answer in fact was useless, with no details and looked more like an attempt to pretend they cared. I'm sure, their expectations for unpaid 1 week task were absolutely disproportional. I'm far from directly accusing them of mining the ideas for free, but the overall situation indeed made me suspect them. Beware!